Chemical composition for producing heat



United States Patent Office Patented Nov. 10, 1964 The present inventionrelates to compositions of matter which react to produce heat, and theprimary object of the invention is to provide a fluid composition which,when dispensed onto a hot surface, reacts exothermically withoutappreciable gaseous by-products. Thus, the composition of the presentinvention is adapted for use in a closed system where it would beinconvenient or impossible to dispose of combustion products.

Another object of the invention is to provide a completelyself-contained composition that reacts with the evolution of largequantities of heatwithout consuming oxygen which may be in limitedsupply, as in a submarine or space capsule. A typical application of thepresent invention would be for under-sea power supply packages, in whichthe heat output of the composition is converted to electricity for thepurpose of charging batteries by means of the Peltier principle, using athermopile, or by thermionic conversion systems.

A further object of the invention is to provide a chemical compositionfor producing heat, which is chemically stable up to 400 F, and which isnon-explosive.

One important advantage of the present invention is that on the basis ofenergy production, the fluid compositions of the invention provide moreheat per unit of volume than any known common propellant or explosive,and, in, fact, provide among the highest outputs known in the chemicalenergy field. This fact, coupled with its high stability andgaslessness, make the compositions of the present invention useful forthe generation of heat in closed systems.

In a broad form of the invention, our heat-producing compositionconsists of a fluid slurry of active, finely powdered metals selectedfrom the group consisting of lithium, aluminum, magnesium, sodium,potassium, rubidium, caesium and beryllium, or alloys thereof, suspendedin a fiuorochlorocarbon oil, such as Kel-F, manufactured by MinnesotaMining & Mfg. Co., or Fluorolube, manufactured by Hooker ElectrochemicalCorp. Preferably, the powdered metal includes a minor proportion oflithium, either as a pure metal or in the form of an alloy with one ofthe other metals named; in which the lithium constitutes approximately3% to 4% of the total weight of the composition, while the other metalor metals constitutes approximately 21% to 22% of the total weight, andthe fiuorochlorocarbon oil constitutes approximately 75% of the weight.The lithium, being an extremely active metal, tends to react first withthe fiuorochlorocarbon oil, and the heat of its reaction serves toinitiate the reaction of the less reactive metal.

The exact structure of the fiuorochlorocarbon oil is somewhat variable,and is generally shown as (C F Cl) wherein the subscript n representsthe number of molecules linked together to form a chain. Thesefluorochlorocarbon oils have densities ranging from 1.8 to 2.1, andtherefore in order to maintain a stable dispersion of finely powderedmetal in the oil, it is necessary that the metal or alloy be ofapproximately the same density as the oil. Aluminum is the preferredmajor constituent of the powdered metals because the density of itsalloys useful for this application approximates that of thefluorochlorocarbon oil. Since lithium is the lightest metal known, witha specific gravity of only 0.53, it is preferable to use an alloy oflithium and aluminum, or lithium and one of the other metals in thegroup named hereinbefore. The incorporation of 0.2% to 0.3% of a veryfine silica, in the range of 0.01 to 0.03 micron particle size improvesthe combusion efliciency and retards settling of the metal.

Example 1 A fluid slurry consisting of by weight of fluorochlorocarbonoil, 22% by weight of finely powdered aluminum, and 3% by weight offinely powdered lithium, was thoroughly mixed to produce a uniformdispersion. This slurry was dispensed slowly onto a hot surface at 600F., with the following dual reaction:

The above two reactions are exothermic, and the amount of heat given offby the reactions is expressed by the following thermochemical equations,where the molar ener gies represent heats of formation of the reactantsand products:

Heat of reaction (l)=565 kcal./rnol The atomic weights of the elementsinvolved in the above reaction are:

The gram molecular weights of the fluorochlorocarbon oil and aluminumentering into the reaction are as follows:

3 (C F CI) 4A1 349.44 gms.+:107.92 gms.=457.36 gms. 457.36 gms. yields565 kcal.

Converting from kcal./mol to cal./ gm. gives:

565 kcal./mol=1235 cal/gm.

The thermochemical reaction of lithium with fluorochlorocarbon oil is asfollows:

(2) C F Cl+4Li 3LiF+LiC1+2C 196 kcal./moi) +O 3 145.6 kcal./mol) (-97.65kcal./mol) +0 l96 kcal./mole -534.45 kcal./mol

Heat of reaction (2)=338.45 kcal./mol

The molecular weight of Li is 6.94, and the gram molecular weights ofthe fluorochlorocarbon oil and lithium entering into the reaction are asfollows:

116.46 gms.-|-27.76 gms.=144.22 gms. 144.22 gms. yields 338.45 kcal.

Converting from kcal./mol to cal./ gm. gives:

338.45 kcal./mol=234l caL/gm.

As there is roughly seven times as much aluminum by weight as there islithium in the composition, the combined heat of the reaction betweenthe two metals and the fluorochlorocarbon oil is approximately 1275calories per gram of lithium/aluminum/fiuorochlorocarbon slurry.

3 Example- 2 A slurry of finely divided lithium/ aluminum alloy wasdispersed in fluorochlorocarbon oil, at the ratio of 25 parts by weightof alloy to 75 parts by weight of fluoroch lorocar bon oil. The alloyconsisted of 14.8% by weight of lithium, and 85.2% by weight ofaluminum. Thus, thelitliium is 3.7% of the total formulation. Dispenseddropwise onto a hot plate, the chemical reaction is substantially thesame as in Example 1, except that a somewhat higher heat output of 1399cal./ gm. is obtained, due to the higher content oflithium.

Example 3 A slurry was prepared by dispersing a finely divided ternaryalloy of lithium, magnesium and aluminum, together with a small'quantity of colloidal silica ranging in particle size from 0.01 to 0.03microns, in fluorochlorocarbon oil in the proportions of 25% by weightof alloy, 74.8% fluorochlorocarbon oil, and 0.2%- colloidal silica. Thealloy consisted of by Weight of lithium, 18%- magnesium, and 72%aluminum. When dispensed dropwise on a hot plate of over 600 F., theslurry reacted thermochemically, with the evolution of large quantitiesof heat without appreciable gaseous by-products.

The reaction of the lithium and aluminum in the alloy with thefluorochlorocarbon oil is as given in Example 1, while thethermochemical reaction of the magnesium with the fluorochlorocarbon oilis as follows:

Themolecular weight of Mg is 24.32, and the gram molecular weights ofthe fluorochlorocarbon oil and magnesium entering into the reaction areas follows:

2 s 232.'96+97.28=330.24 gms. 330.24 gms. yields 551 kcal.

Converting from kcal./mol to cal./ gm. gives:

551 kcaL/mol: 1670 cal/gm.

V The colloidal silica does not enter into the reaction, but

retards settling, of the alloy and improves combustion efiiciency.

Obviously, many modifications andvariations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore only such-limitation should be imposed asare indicated in the appended claims.

We claim:

1. A composition for producing heat without appreciable gaseousby-products when dispensed drop-wise onto a hotsurface,.saidcompositionconsisting of a fluid slurry of finely dividedmetals in afiuorochlorocarbon oilcontaining fluorine, chlorine, and carbon atoms inthe approximate ratios shown by the formula C F CI, said metalsconsisting of lithium in the proportion of about 3% to 4% of the totalweight and aluminum in the proportion of about. 21% to 22% of the totalweight.

2. A composition for producing heat without appreciablegaseous'by-products when dispensed dropwise onto a hot surface, saidcomposition-comprising a fluid slurry. of a finely divided metal in afluorochlorocarbon oil containing-fluorine, chlorine, and carbon atomsin the approximate ratios shown by formula C F Cl, said metal consistingof a lithium/ aluminum alloy in which lithium is about '15 by weight ofthe total metal, and the remainder is aluminum, said finely dividedmetal being in the proportion of about 25% of the total weightof thecomposition, and said fiuorochlorocarbon oil being in the proportion ofabout of the-total weight.

3. A composition forproducing heat without appreciablegaseous-by-products when dispensed onto a hot surface having atemperature above 600 F., said composition comprising afluid slurryconsisting of about 25% by weight of a finely divided ternary alloy oflithium, magnesium and aluminum, together with about 0.2% of colloidalsilica dispersed in a fluorochlorocarbon oil containing fluorine,chlorine, and czu'bon atoms in approximate ratios shown by the formula CF Cl, said alloy consisting of about 10% by weight of lithium, about 18%magnesium, and about 72% aluminum.

4. A fluid composition for producing heat without gaseous by-productswhen ignited ina closed system, said composition consisting of an alkalimetal selected from the group consisting of lithium, sodium, andpotassium; a light metal-selected from the group consisting of aluminum,magnesium, and beryllium; and. a fluorochlorocarbon oil containingfluorine, chlorine, and carbon atoms in the approximate ratios shown bythe formula C F Cl, said alkali and light metals together constitutingabout 25 of the total weight.

5. A fluid composition for producing heat without geseous by-productswhen ignited in a closed system, said composition consistingof about 3%to 4% by weight of lithium; about 21% to 22% by weight of a light metalselected from the group consisting of aluminum, magnesium, andberyllium; and the remainder of a fluorochlorocarbon oil containingfluorine, chlorine, and carbon atoms in the approximate-ratios shown bythe formula C F Cl.

FOREIGN PATENTS Great Britain May 29, 1919

4. A FLUID COMPOSITION FOR PRODUCING HEAT WITHOUT GASEOUS BY-PRODUCTSWHEN IGNITED IN A CLOSED SYSTEM, SAID COMPOSITION CONSISTING OF ANALKALI METAL SELECTED FROM THE GROUP CONSISTING OF LITHIUM, SODIUM, ANDPOTASSIUM; A LIGHT METAL SELECTED FROM THE GROUP CONSISTING OF ALUMINUM,MAGNESIUM, AND BERYLLIUM; AND A FLUOROCHLOROCARBON OIL CONTAININGFLUORINE, CHLORINE, AND CARBON ATOMS IN THE APPROXIMATE RATIOS SHOWN BYTHE FORMULA C2F3CL, SAID ALKALI AND LIGHT METALS TOGETHER CONSTITUTINGABOUT 25% OF THE TOTAL WEIGHT.